Sidewall sampling apparatus



p 13, 1965 A. J. TRICON ETAL 3,272,253

SIDEWALL SAMPLING APPARATUS Filed May 25, 1965 4 Sheets-Sheet 1 CONTROL EQUIPMENT INVENTORS ALFRED J. TRICON BY FORREST v. PORTER 5 g/fia/wfl ATTORNEY p 13, 1966 A. J. TRICON ETAL 3,272,263

SIDEWALL SAMPLING APPARATUS 4 Sheets-Sheet 2 Filed May 25, 1965 .INVENTORS. ALFRED J. TRICQN ATTORNEY p 13, 1966 A. J. TRICON ETAL 3,272,268

I SIDEWALL SAMPLING APPARATUS Filed May 25, 1965 4 Sheets-Sheet 5 INVENTORS ALFRED J. TRlGON FORREST V. PORTER ATTORNEY p 1966 A. J. TRICON ETAL SIDEWALL SAMPLING APPARATUS 4 Sheets-Sheet 4 Filed May 25, 1965 FIG.6

m O N E V W ALFRED J. TRICON BY FORREST V. PORTER FIG] ,AI TORNEY United States Patent O 3,272,268 SIDEWALL SAMPLING APPARATUS Alfred J. Tricon and Forrest V. Porter, Houston, Tex.,

assiguors to Dresser Industries, Inc., Dallas, Tera, a corporation of Delaware Filed May 25, 1965, Ser. No. 461,598 12 Claims. (Cl. 175-4) This is a continuation-in-part of the copending application Serial No. 189,425, filed April 23, 1962, by Alfred J. Tricon and For-rest V. Porter, and now abandoned.

This invention relates to methods and apparatus for obtaining samples of subsurface substances traversed by a borehole, and more particularly relates to improved methods and apparatus for penetrating the wall of the borehole to obtain such samples.

It is well known that oil and gas, and other related natural substances generally included Within the term petroleum, are usually found in formations or strata of earth or rock below the surface of the earth, and that recovery of these substances is generally achieved by means of a borehole which is drilled in a manner to tap these formations. Atlhough various techniques are available for gaining information with respect to the location and character of strata underlying previously undrilled areas of the surface, such information is only approximate. Thus, other techniques are often utilized during and after drilling operations to obtain samples of the material being penetrated. One well-known technique for obtaining these samples includes cutting a core of the rock or earth by means of a tubular shaped drill bit fixed at the bottom of the drilling string. This method takes a long time, however, and is therefore expensive since each time a core is to be taken and raised to the surface, the entire drilling string must first be removed from the borehole. Thus, cores are generally taken only at limited intervals throughout the drilling operations.

A sampling technique which may be performed at substantially less cost involves the use of a wireline-type tool for selectively taking samples from the wall of the borehole at any desired level. This tool, which is commonly known as a sidewall sampler, generally includes an elongated shaft containing along its length a plurality of traverse apertures which function in the manner of short gun barrels, and having in each such barrel an explosive charge and a projectile adapted to be laterally discharged thereby into the wall of the borehole. Provision is also generally included for electrical circuitry for achieving the ignition of the charges from a control point at the surface. Further, since the cores taken by the projectiles are intended to be recovered, the projectiles are generally coupled to the aforementioned shaft by means of one or more small cables. Thus, when the shaft is withdrawn from the borehole, these cables permit the projectiles containing cores to be thereby pulled out of the borehole wall and carried to the surface along with the shaft.

In operation, the sidewall sampler may be lowered by means of conventional cabling and hoist equipment to that section of the borehole which is adjacent the formation sought to be sampled. Thereafter, one or more of the guns may be fired to discharge corresponding projectiles laterally into the adjacent substances. When the sampler is drawn up the borehole, the aforementioned small cables which remain attached to both the sampler and the imbedded projectiles serve to drag the projectiles out of the formation, as the sampler is drawn up the borehole.

Notwithstanding the advantages of selectivity and speed of sampling afforded by the sidewall sampler, several problems exist which presently limit its utility. For example,

3,2 72,268 Patented Sept. 13, 1966 the adjacent formation may be composed of a relatively non-porous or hard substance such as granite. In such a case, the projectile may not penetrate the face of the borehole wall with sufiicient force to obtain a representative sample of the substances to be investigated. On the other hand, if a porous substance is encountered the projectile may be driven so deeply into the formation that the small ca'bles attached thereto are snapped. The prior art has attempted to solve this problem by utilizing projectiles of selectively different design when formations of different porosity and hardness are to be sampled. For example, in the case of harder substances a somewhat pointed projectile may be used which has a relatively small diameter and a sharp, serrated cutting edge. On the other hand, projectiles of relatively larger diameter and relatively blunt cutting ends may be preferred for more porous formations. Although the use of sharp nosed projectiles of small diameter has somewhat improved the capability of the sidewall sampler to obtain samples of harder formations, even the bluntest projectiles are still frequently lost in the softer formations.

It will be apparent that, if the explosive charge used to propel the coring projectile could be selectively varied, the depth of penetration of the projectile might be effectively controlled to prevent the linking cables from being severed. However, it should be remembered that the aforementioned elongated body is seldom greater than about four inches in diameter, and thus the gun barrels are very short at best. In order to effectively utilize such barrel length as is available, the firing chambers of each gun are now generally located so as to dispose the propelling charge annularly about the coring projectile in the manner depicted in FIGURE 3, of US. Letters Patent 2,848,195, issued August 19, 1958, to Forrest V. Porter. Apparatus of such character does, in fact, permit the maximum effective barrel length possible with such small diameter bodies. However, such equipment must be substantially disassembled for loading and re-loading purposes, and therefore the propelling charges may not be conveniently adjusted, or even replaced, in the field. Moreover, in order to insure contact, the igniter material which is used to explode the propellant is attached to, and made a permanent part of, the electric terminal in the firing chamber, by which means electric current is applied to the igniter material. Thus, it is also necessary to replace the terminal as well as the propelling charge in each gun, before it can be re-armed, and this operation is also not conveniently performed in the field.

Notwithstanding the fact that many projectiles are presently lost by being discharged with excessive force, it should be clearly understood that much of the energy developed in the firing chambers of conventional sidewall sampling equipment is completely wasted. This waste is primarily due to the fact that the gun barrels are relatively very short, as hereinbefore explained, and thus the expanding gases developed by the ignited propellant are trapped in the gun barrel by the projectile only as long as the projectile occupies the gun barrel. However, a significant amount of such energy is also lost due to escape of much of these gases while the projectile is still in the gun barrel. In more conventional types of forearms, this gas loss is substantially reduced by the use of projectiles which are adapted to cooperate in some manner with the bore of the gun to seal in the gases. This is generally accomplished by using a projectile which is soft relative to the rifled bore of the gun, or a projectile which has one or more encircling rings or hands of relatively soft material, and which soft projectile or bands are deformed by the grooves of the r-irfling as the projectile passes out of the gun. Such projectiles may only be used once, and therefore are not suitable for adaptation to use in sidewall sampling apparatus of conventional 3 design, since it is more economical to waste propellant than to replace projectiles of the subject character after each firing. In addition, however, sidewall sampling guns must be smoothbore in character, and thus there is no way in such apparatus to effectively deform the projectiles without substantially retarding their travel through the gun barrels.

These disadvantages of the prior art are overcome with the present invention, and novel methods and apparatus are provided for more efficiently and effectively obtaining sidewall samples of subsurface substances traversed by a borehole.

Accordingly, it is an object of the present invention to provide novel methods and apparatus for conserving and controlling the force used to explosively discharge a sampling projectile from sub-surface apparatus disposed in a borehole in the earth.

It is another object of the present invention to provide novel methods and apparatus for selectively varying the force used to explosively discharge a sampling projectile from sub-surface apparatus disposed in a borehole drilled in the earth.

It is another object of the present invention to provide improved sub-surface sidewall sampling apparatus which may be quickly re-armed without the necessity of substantial disassembly of the apparatus.

-It is a further object of the present invention to provide novel methods and apparatus for explosively discharging a sampling projectile at an increased velocity from a smoothbore gun device having a relatively short barrel.

It is another object of the present invention to provide novel apparatus for explosively discharging a sampling projectile into the sidewall of a borehole, said apparatus including provision for said discharged projectile to substantially retain expanding gases within said apparatus while said projectile is at least partly contained in said apparatus.

It is another object of the present invention to provide novel method for obtaining a sample of a subsurface earth formation traversed by a borehole, said method comprising the steps of disposing in said borehole a gun loaded with a hollow projectile which is coupled to said gun by a flexible linking means of preselected length, aiming said gun toward said earth formation, discharging said projectile into said earth formation with a preselected force functionally related to the consolidation of said earth formation whereby said projectile penetrates said formation a distance great enough to fill with earth from said formation but not great enough to sever said link, and thereafter drawing said gun and said projectile from said earth formation and borehole.

It is a feature of the present invention that the firing chamber be located immediately behind the projectile loaded in the gun, and that this firing chamber be adapted to accommodate a cartridge containing a fixed charge of explosive.

It is another feature of the present invention that the base of the projectile be inwardly hollowed in a concavelike manner to provide a cavity for receiving additional explosive in such quantities as may be accommodated therein, so that the size of the firing chamber is thereby enlarged without any foreshortening of the effective barrel length of the gun resulting from such enlargement.

It is another feature of the present invention that the aforementioned hollowed base be detachable from the projectile, so that a base having a cavity of one size may be exchangeable with another base having a different size cavity, so that the extent of such enlargement of the firing chamber may be changed as desired.

It is a further feature of the present invention that the hollowed base be provided with a vent aperture having a replaceable stoppering means.

It is also a feature of the present invention to house the base load of propelling charge in a cartridge case, and that at least a part of such case be adapted to form a substantially gas-tight seal about the base of the projectile as such projectile and base is discharged from the gun.

It is a further feature of the present invention to include the igniter material within the cartridge case containing the base charge, and to provide the base charge with a cavity adjacent the contact terminal of the gun.

These and other objects and features of the present invention will be apparent from the following detailed description wherein reference is made to the figures of the accompanying drawings.

The advantages of the present invention are preferably attained by means of sidewall sampling apparatus having provision for one or more guns of smoothbore, muzzleloading character. Each gun is provided with a sampling or coring projectile which may be slidably inserted therein in a relatively gas-tight manner, so that expanding gases produced by ignition of a propelling charge of explosive will effectively discharge the projectile. The firing chamber in each gun is located immediately behind the projectile, and is of a size and shape to accommodate a socalled minimum or base load of explosive of a predetermined shape and volume. The exterior surface of the butt or base of the projectile is preferably inwardly hollowed in a concave-like manner, so that when the projectile is disposed in the gun this hollowed surface provides an enlargement of the firing chamber. Thus, additional amounts of explosive may be inserted in this enlargement to increase the total amount of propelling charge in the gun. This base end of the projectile is preferably detachable, so that the size of the aforementioned enlargement may be altered by the substitution of different bases as desired. The base end of each projectile also preferably includes a vent to permit air to escape from behind the projectile while it is being inserted in the gun barrel, and means such as a screw for stopping or closing this vent after the projectile is loaded in the gun.

In order to protect the base load from being damaged when the projectile is inserted into the gun barrel, the base load is preferably contained in a cartridge case. The end of the cartridge case, which faces the hollowed base of the projectile, should be provided with one or more apertures to facilitate ignition of the additional charge by the base charge, so that ignition of the total propelling charge is uniformly accomplished. This perforated end is preferably secured to the cartridge case by means of a ring-like cap of a material such that this cap will be driven against, and will follow, the base of the projectile out of the gun barrel. In this manner, the cap ring provides an improved gas seal to prevent escape of significant amounts of the expanding gases generated, and to thereby insure that substantially the full force of the explosion will be applied to the discharge of the projectile.

As in conventional equipment, the igniter material used to explode the base charge is itself ignited by an electric current delivered from the earths surface, through the cable, to a contact terminal protruding into the firing chamber of each gun. In the present invention, this contact terminal may be the head of an insulated screw disposed in the block of the gun, and the cartridge case should include provision for accommodating this screw head in a manner to prevent the base charge from being urged thereagainst by the insertion of the projectile into the gun. This provision is preferably attained by means of a base load having a cavity, and by means of a flexible electric contact which yields to the contact terminal. The igniter material is preferably included in the cartridge, rather than mounted on the contact terminal as in conventional equipment, and thus the contact terminal need no longer be replaced after each firing as is the case with conventional equipment.

In the drawings:

FIGURE 1 is a pictorial view, partly in cross-section, of a sidewall sampler disposed in a typical borehole.

. FIGURE 2 is a view of a coring projectile which has been discharged into an adjacent formation.

FIGURE 3 is a view taken partly in cross section of the sidewall sampler and projectile along line AA in FIG- URE 1 and showing a preferred form of the present invention.

FIGURE 4 is a more detailed view of the sidewall sampler and projectile illustrated in FIGURE 3 with certain portions of the sampler shown in elevation in that figure shown in cross section and showing particular features of the preferred form of the present invention.

FIGURE 5 shows a modification of a part of the propelling charge suitable for purposes of the present invention.

FIGURE 6 shows another modification of the propelling charge suitable for purposes of the present invention.

FIGURE 7 shows a further modification of the propelling charge suitable for purposes of the present invention.

In that form of the present invention chosen for purposes of illustration in the drawings, FIGURE 1 shows a typical borehole 2 drilled into the earth 3 and containing a sidewall sampler 4 suspended therein by a cable 6, which is secured to the sidewall sampler 4 by means of a cable head 5 and which cable 6 may be of conventional design to include one or more electrical conductors as desired. The cable 6 is connected to control equipment 8 located at the surface, and is also used to pass the sidewall sampler 4 in and out of the borehole 2. The depth at which the sidewall sampler 4 is disposed may be determined by means of a measuring wheel 9, from which the cable 6 is suspended, and over which the cable 6 is drawn by conventional means not shown in FIGURE 1. The measuring wheel 9 may be suspended in any convenient manner, such as by a traveling block suspended over the mouth of the borehole 2 by a derrick.

As shown, the sidewall sampler 4 includes an elongated body 10 having a plurality of projectiles 12 arranged in a manner to be discharged laterally into the wall of the borehole 2 as will hereinafter be explained in greater detail. As illustrated in FIGURES 1 and 2, each projectile 12 is also connected to the body 10 by means of one or more cables 14 or other type of flexible linking means of some suitable design. Referring to FIGURE 2, there is depicted therein a section of the borehole 2 and body 10 hereinbefore mentioned, wherein the projectile 12 has been discharged into the wall of the borehole 2 in a manner to take a sample of the adjacent earth 3. As shown in FIGURES l and 2, the projectile 12 is provided with an enlarged cutting edge 16 to cut a corehole 18 of a diameter larger than that of the body of the projectile 12 to prevent the projectile 12 from becoming too tightly imbedded in the more impacted formations of the earth 3. The attached cables 14 should be long enough to permit the projectile to penetrate the earth 3 a depth suflicient to pass beyond any drilling mud which may be deposited on the face of the wall of the borehole 2. However, when the body 10 is drawn out of the borehole 2, the cables 14 will serve to pull each projectile 12 out of its respective core hole 18, and to carry it upwards, in order that the cores contained in each projectile 12 may be recovered at the surface for testing and analysis. It is thus apparent that, since boreholes 2 such as that depicted in FIGURES 1 and 2 are of a relatively small diameter, the body 10 must of necessity be even smaller in diameter and, consequently, the gun barrel 20 of each gun 11 must be at least somewhat shorter in length than the diameter of the body 10, in order to provide a block 53 as hereinafter described.

Referring now to FIGURES 3 and 4, there may be seen a partially cross sectional view of the body 10 taken along line AA in FIGURE 1 which depicts a typical gun 11 loaded with a typical projectile 12. As shown, the gun 11 proper is composed of a gun barrel 20 of a smoothbore character, a firing chamber 52, and a block 53. Since the gun 11 is adapted to be loaded through its muzzle,

the block 53 may be fixed in the manner of any muzzleloading type of gun, rather than removable in the manner of a breech-loading gun. As shown, the projectile 12 is composed of a hollow core barrel 24 having threaded apertures 26 for attaching the linking cables 14 referred to and depicted in FIGURES 1 and 2, and includes a slideably detachable cutting nose 28. The afore-mentioned linking cables 14 may be attached to the body 10 at sockets 27. A cutting nose 28 of the type shown is particularly useful, though not necessarily essential, in aiding in the recovery of the core barrel 24 after its discharge into the adjacent wall of the borehole 2, since it carves out a corehole 18 of a diameter larger than that of the core barrel 24. Although the cutting nose 28 may become firmly imbedded in the formation, the core barrel 24 may be easily pulled free of the cutting nose 28 and out of the core hole 18 when the body 10 is withdrawn; from the borehole 2. In some circumstances it may be more desirable to use projectiles 12 which do not employ such a cutting end.

As may be seen in FIGURES 3 and 4, the complete projectile 12 includes not only the core barrel 24 and cutting nose 28, but also a preferably detachable base 22 which is adapted to be discharged with the core barrel 24 as an integral part of the projectile 12, and which is shown attached to the core barrel 24 to facilitate removal of the core from the interior of the core barrel 24 after discharge and recovery of the projectile 12. It is preferable that, as depicted in FIGURES 3 and 4, the base 22 is also provided with a threaded aperture or vent 30 containing a slotted or socket-headed screw 32 and a gasket 34 as a stoppering means, and may also have a small upper recess 36 for more securely holding the head of the screw 32. Although the gun barrel 20 is generally smoothbore in character, the projectile 12 is preferably fashioned in a manner to fit as snugly as reason-ably possible in the gun barrel 20 in order to prevent any avoidable loss of pressure from the discharging explosion. Because of this tight fit, such a projectile 12 would be difficult to insert in the gun barrel 20 due to compression of air trapped within the gun barrel 20. To avoid this factor, the slotted screw 32 is preferably first removed to allow this air to escape through the vent 30, and then replaced to prevent loss of pressure generated by the explosion. The gasket 34 is also desirable to aid in effectively sealing the screw 32 in the vent 30 to prevent borehole fluids from entering the firing chamber 52.

It may be seen in FIGURES 3 and 4 that the base 22 is preferably equipped with a ring-type gasket 40 in a circumferential groove 38 or seat, to further provide against loss of pressure generated by igniton of the propelling charge, and to prevent borehole fluids from entering the firing chamber 52. In addition, a bottom gasket 42 may be employed which is preferably adapted to follow the discharged projectile 12 out of the gun barrel 20 in a manner to continue to aid in sealing in the explosion pres sure as long as some part or extension of the projectile 12 occupies the gun barrel 20.

Another important feature of the present invention is the adaptation of the base 22 to provide a cavity or hollow section in that part which is adjacent the firing chamber 52 of the gun barrel 20. This cavity 50 is preferably fashioned in a manner such that an elongated projection or skirt 54 is provided for the base 22 in order to maintain as much of the projectile 12 as possible within the gun barrel 20 notwithstanding this effective enlargement of the firing chamber 52. As depicted in FIGURES 3 and 4, the propelling charge used to discharge the projectile 12 may be composed of a base charge of a magnitude to be accommodated by a firing chamber 52 of conventional size and design. In addition, one or more pellets 62 of explosive, of suitable size and shape, may be added to increase the total propelling charge as desired. Since the cavity 50 effectively provides an enlargement of the firing chamber 52, such pellets 62 may be added as shown in FIGURES 3 and 4 'without any foreshortening of the effective length of the gun barrel 20 thereby resulting, which would otherwise be the case with equipment of conventional design. The base load 60 may be in the form of a solid cake for purposes of easy handling and loading, and is preferably ignited by means of an electric charge delivered to an electric contact 64 as hereinafter explained in detail.

Reference may now be had to FIGURE 4 for a more detailed view of the firing chamber 52 containing the base load 60. As hereinbefore stated, the so-called fixed or base load 60 proper may be composed of a block or cake of explosive. Since such a cake is often somewhat fragile, the base load 60 is preferably enclosed in a ring-shaped, electrically non-conductive cartridge case 70 having an aperture 74 as shown in the drawings. The bottom side of the cartridge case 70 is preferably fashioned in the manner of a flexible plate or disc 72, from a thin sheet of metal such as copper. The top of the cartridge case 70 (as viewed in the drawings) is preferably formed of a soft-metallic cap ring 42 which is secured in some suitable fashion to the cartridge case 70 to hold a so-called top plate or disc 73 adjacent the opposite side of the base load 60. Neither the top or bottom discs 72 and 73 need a-ctually be round in shape, since they may be square, polygonal, star-shaped, or have any other suitable shape. It is the purpose of the aforementioned aperture 74, in the cartridge case 70, to provide for direct electrical contact between the bottom disc 72 and the contact 64 protruding from the block 53 of the gun 11. Thus, electric current flowing to the contact 64 may be conducted through the bottom disc 72, and through an igniter wire 76 connected thereto, to ground (the shaft by way of a conductive tab 78 which may be interposed around the non-conductive cartridge case 70. Ignition of the base load 60 may be facilitated by provision of a suitable igniter material (not specifically shown) around or adjacent the igniter wire 76. Ignition of any pellets 62 used may be facilitated by the provision of one or more perforations or apertures in the top disc 73.

As herein-before mentioned, the explosive charge is fired by means of an electric current passing to the electric contact 64. That is, when the current is delivered by way of the cable 6 shown in FIGURE 1 to the contact 64 shown in FIGURE 3, it passes to and through the disc 72, the igniter wire 76, and the tab 78 to fire the aforementioned igniter material and, consequently, to ignite the base load 60 and such pellets 62 in the firing chamber 52 and cavity 50 as may constitute the propelling charge. The pressure of the expanding gases produced by the explosion serve to drive the core barrel 24, the cutting nose 28, the base 22, the ring gasket 40, and the bottom gasket 42, out of the gun barrel toward the adjacent formation.

As has been hereinbelfore mentioned, the gun barrel 20 is relatively short. Thus, it is essential that the expanding igases developed by the ignition of the propelling charge be prevented from escaping from the gun barrel 20 until after the projectile 12 has been discharged therefrom. In order to retain these gases behind the projectile 12 during its travel through the gun barrel 20, several sealing features have been incorporated into the present invention disclosed in the figures of the accompanying drawings, such as the provision of the aforementioned ringtype gasket 40 disposed about the base 22. A particular feature may be found in the cooperation of the cap ring 42 to form a gas seal after the propelling charge has been ignited. This function may be obtained by utilizing a cap ring 42, which is fashioned from a malleable material such as copper, and which is thereby capable of being pressed against the gun bar-rel 20 and the base 22, by the ignition of the propelling charge, so tightly as to form a very effective gas-tight seal. By adhering tightly to the base 22 While the projectile 12 is driven out through the gun bar-rel 20, the distorted cap ring 42 follows the projectile out of the gun barrel 20 and thus continues to seal in the expanding gases generated by the explosion to increase the muzzle velocity of the discharged projectile 12.

Reference may also be had to FIGURE 4 wherein may be seen the details of the various parts of electrical contact 64 and its associated circuitry. Connection with the aforementioned bottom disc 72 is preferably accomplished by means of the head of a screw 80, which is formed of a conductive metal or some other suitable material, and which is mounted in a hole 84 in the block 53 at the rear of the gun barrel 20 and firing chamber 52. It cannot be over-emphasized that extraordinary pressures are developed (at least momentarily) in the firing chamber 52 by the ignition of the propelling charge composed of the base charge 60 and pellets 62. Thus, the hole 84 is preferably fashioned in the manner of a sloping recess to accommodate a screw having a head with sloping shoulders, as depicted in FIGURE 4, so that the screw 80 will be effectively seated within the hole 84 by the explosion to prevent the escape of any of the expanding gases. Insulation of the screw 80 from the block 53 is provided by a small ring-type gasket 82 which also aids in sealing of escape of the aforementioned expanding gases through the hole 84, and also prevents entry by borehole fluids through the hole 84 to the firing chamber 52 before ignition of the propelling charge. The shank 81 of the screw 80 may also be kept from electrical contact with surrounding portions of the block 53 'by means of another small ring-type gasket 86.

Apparatus found particularly suitable to the purposes of the present invention include a ceramic insulator 88, a second relatively thin insulator 90, and an electric terminal 92. The ceramic insulator 88 is disposed about the shank 81 of the screw 80 in a manner to support the second insulator 90 in association with the terminal 92. It is the function of the terminal 92 to afford a suitable means by which electric current may be connected to the shank 841 of the screw 80 to ignite the base load 60. Thus, as shown in FIGURE 4, an insulated lead 83 is connected to the terminal 92 to extend through a passage in the body 10 in any suitable manner to the cable 6 depicted in FIGURE 1.

Also shown in FIGURE 4 is a cap 96, which is preferably formed of some resilient material such as rubber, and a metal button 98. It is the function of the cap 96 and button 98 to further insure that contaminants such as borehole fluids do no enter the firing chamber 52 by way of the hole 84, and also to provide a ready access to the various components of the contact 64 for purposes of repair or replacement. It is particularly desirable that the cap 96 be (formed to fi-t snugly about the nut 94, and the small end of the shank 81 of the screw 80, so that the nut 94 will be immobilized relative to the screw 80. Thus, the screw 80 and the ring gasket 82 may be removed from the block 53 and replaced without the necessity of disturbing the other components of the contact 64.

Loading any of the guns 11 is a relatively simple and rapid process. First, a base load 60 (contained in a cap ring 42, cartridge case 74), etc.) is inserted through the muzzle'of the gun 11, and into the firing chamber 52, in a manner such that the so-called bottom disc 72 rests against the contact 64, and such that the tab 78 is brought into physical contact with the block 53 (or some other portion of the body 10). Next, one or more pellets 62 are added as desired, and are positioned adjacent the perforated top disc 73. Thereafter, the screw 32 is preferably removed from the vent 30 in the base 22, and the projectile 12 is inserted through the muzzle of the gun 11 along the gun barrel 20, until the skirt 54 of the base 22 presses firmly against the cap ring 42. Finally, the screw 32 is replaced in the vent 30 in the base 22.

As has hereinbefore been stated, the base load 60 is preferably formed in the manner of a cake. Thus, if the base load 60 is fashioned with a relatively fiat bottom surface as depicted in FIGURE 3, the base load 60 may be crushed against the contact 64, which protrudes from the block 53, when the projectile 12 is inserted in the gun 11. On the other hand, it is essential that the projectile 12 be pressed firmly against the cap ring 42 surrounding the base load 60 so that the bottom disc 72 and tab 78 are brought into good electrical contact, respectively, with the contact 64 and the body 10. Thus, it is preferable that the surface of the base load 60, which is adjacent the bottom disc 72, be concave in the manner depicted in FIGURE 4.

Referring again to FIGURE 4, there may be seen that the base load 60 contained in a cap ring 42 and insulating cartridge case 70 is provided with a hollow or cavity 61 to an extent necessary to accommodate an expansion of the bottom disc 72 caused by the protrusion of the contact 64. It will be apparent that when the skirt 54 of the base 22 is urged firmly against the cap ring 42, and the cartridge case 70 is forced down around the contact 64, the contact 64 will protrude upward through the aperture 74 to deform the bottom disc 72 into the cavity 61 without crushing the base load 60. In such an arrangement it is preferable that the bottom disc 72 be fashioned of a resilient spring-like metal, so that it will tend to return to its normal shape if the gun 11 is to be unloaded without being discharged.

Referring to FIGURE 5, there may be seen another modification wherein the base load 60-A has been fashioned generally in the manner of a toroid in order that the resilience of the bottom disc 72A may be effectively supplemented by a spring 74-A disposed through the base load 60-A. The spring 74-A is preferably insulated electrically from the bottom disc 72A by means of an insulating disc 75 to provide that electric current passing to the bottom disc 72A from the contact 64 shall pass only through the relatively highly-resistant igniter wire 76 and tab 78 to ignite the base load 60-A. The cartridge case 70 may be formed as depicted in FIGURES 3-4. However, as shown in FIGURE 5, the functions of the cap ring 42 and top disc 73 depicted in FIG- URES 3-4 are preferably combined in a single cover 42-A having a central aperture 43 formed as depicted to support the spring 74-A in a generally fixed position. The cover 42-A may be perforated, as herein before explained for the top disc 73 depicted in FIGURES 3-4, to aid in the ignition of any pellets 62 which may be positioned adjacent thereto.

Referring now to FIGURE 6, there may be seen another modification of the propelling charge wherein the base load 60 and pellets 62 depicted in FIGURES 3-5 have been replaced with a single charge which is preformed so as to substantially occupy the entire space between the breech block 53 and base 22. More particularly, a ring-shaped, electrically non-conductive cartridge case 102 is provided which is substantially the same as the cartridge case 70 depicted in FIGURE 4, and which houses a solid block or cake of explosive charge 100.

It will be noted that charge 100 is a single cake which is pre-formed or moulded with a frustum 106 so as to occupy the cavity 50 as well as the firing chamber 52. Accordingly, the base diameter of the frustum 106 is preferably smaller than the diameter of the portion of the charge 100 housed within the cartridge case 102, so that the cap ring 104 functions to retain the charge 100 when crimped or otherwise secured to the cartridge case 102.

Referring now to FIGURE 7, there may be seen a version of the propelling charge depicted in FIGURE 6 which includes certain features provided for in FIGURE 5, wherein the charge 110 is provided with a frustum 112, and a hole or central aperture 114, and wherein the cap ring 104 is replaced by a soft or thin metal cover 116 which generally encompasses the frustum 112. A spring 10 74-A connected to the cover 116 and pressing against the bottom disc 72-A is provided in the aperture 114 similar to the structure depicted in FIGURE 5, and fulfilling the same purpose. Another aperture 74 is provided in the cartridge case 102 so that electrical contact will be obtained between the bottom disc 72-A and the contact 64. It should be understood that some sort of ignition means, such as the igniter wire 76 and tab 78 will also be used in the propelling charges depicted herein.

Numerous other variations and modifications may obviously be made in the structures herein described without departing from the present invention. Accordingly, it should be clearly understood that the forms of the invention described herein and shown in the figures of the accompanying drawings are illustrative only, and are not intended to limit the scope of the invention.

What is claimed is:

1. Apparatus for sampling a subsurface substance traversed by a borehole, said apparatus including an elongated body having at least one aperture extending laterally and at least partially 'therethrough in a manner to form a gun having a bore, a firing chamber of a predetermined length relative said gun, and a block,

a primary propelling charge disposed in and occupying substantially the entire length of said firing chamber between said block and said bore and including a predetermined primary volume of explosive and electrically-responsive means for igniting said explosive,

a hollow projectile adapted to slidably move in and along said bore of said gun and having an open cutting end for penetrating and taking a core-type sample from said substance,

said projectile also having an open butt end,

linking means interconnecting said body and said projectile,

a base adapted to slidably move in and along said bore of said gun and attached to said butt end of said projectile in a manner to relatively close said butt end and to form a longitudinal extension of said projectile,

said base also being characterized by having an outer surface inwardly hollowed relative to the interior of said projectile and having a vent aperture extending through said hollowed surface to the interior of said projectile,

said projectile and attached base being disposed in said bore of said gun in a manner such that said base is positioned immediately adjacent said firing chamber and said base propelling charge and such that said hollowed surface of said base cooperates in said gun to provide a longitudinal enlargement of said firing chamber capable of receiving and accommodating a secondary propelling charge of explosive,

stoppering means arranged in a removable and replaceable manner in said vent aperture in said base,

means arranged and adapted to provide a substantially gas-tight seal between said base and said bore,

an electric contact means disposed in said block in a manner to electrically connect with said electricallyresponsive means for igniting said predetermined volume of explosive in said primary propelling charge,

and means arranged and adapted to pass said body longitudinally through said borehole, including means for providing an electric current to said electric contact means.

2. The apparatus described in claim 1 wherein said primary propelling charge is housed in a case comprising an electrically non-conductive container means adapted to support said predetermined primary volume of explosive and said electrically-responsive means for igniting said explosive and adapted to expose at least a part of said means for igniting to directly contact said contact means,

1 1 and a covering means fixed about said container in a manner to further support said predetermined volume of explosive and adapted to facilitate ignition of any secondary propelling charge of explosive accommodated by said hollowed surface of said base.

3. The apparatus described in claim 2 wherein said primary volume of explosive is formed in the manner of a relatively solid mass having an aperture located -to accommodate said contact means,

and said electrically-responsive means for igniting said primary volume of explosive includes an electrode adapted when urged against said contact means to be resiliently displaced into said aperture in said primary charge of explosive.

4. The apparatus described in claim 2 wherein said means for providing a gas-tight seal includes a resilient body circumferentially disposed abou-tsaid base and adapted to move slidably along said bore with said base.

5. The apparatus described in claim 2 wherein said covering means is also arranged and adapted to be driven against said base and said bore by such ignition of said primary propelling charge in a manner to afford said firing chamber a substantially gas-tight seal at said base and said bore as said projectile and base moves slidably through said bore of said gun.

6. The apparatus described in claim 2 wherein said electrically-responsive means for igniting said primary volume of explosive includes an electrical conductor arranged and adapted in said container means in a manner to be urged into electrical connection only with said contact means disposed in said block, and

an igniter wire arranged and adapted to be interconnected electrically between said electrical conductor and said body and further adapted to provide a relatively high resistance to any electric current.

7. Apparatus for sampling a subsurface earth formation traversed by a borehole, said apparatus including an elongated body having at least one lateral aperture extending at least partially into said body in a manner to form a gun having a bore and the basic portion of a firing chamber,

a hollow projectile having an open cutting end and a base end having an inwardly hollowed outer surface containing a vent aperture,

said projectile being slidably disposed in said bore of said gun in a manner such that said base end cooperates to form an enlargement of said firing chamber,

stoppering means removably disposed in said vent aperture in said base end of said projectile,

means interconnected with said base end of said projectile to form a substantially gas-tight seal for said firing chamber,

linking means interconnecting said body and said projectile,

a primary charge of explosive disposed in said gun so as to substantially occupy said basic portion of said firing chamber but not extending into said enlargement of said firing chamber, and

electrical means for igniting said primary charge of explosive in said basic portion of said firing chamber.

8. In apparatus for sampling a subsurface substance traversed by a borehole; said apparatus comprising an elongated body having at least one aperture extending laterally and at least partially therethrough in a manner to form a gun having a bore' and a primary firing chamber of a predetermined volume,

a primary charge of explosive of said predetermined volume located in said gun and substantially occupying said primary firing chamber,

a hollow projectile having a rear end and a forward cutting end and slidably disposed in said bore of said gun so that said rear end is adjacent said primary charge of explosive,

linking means interconnecting said projectile and said elongated body, and

means in said body for electrically igniting said primary charge of explosive;

the improvement in combination therewith including a base having a vent aperture and an inwardly hollowed exterior surface, and

stoppering means removably located in said vent aperture,

said base being mounted on said rear end of projectile so that hollowed surface provides an enlargement of said firing chamber unoccupied by said primary charge for accommodating a secondary charge of explosive.

9. In apparatus for sampling a subsurface substance traversed by a borehole; said apparatus comprising an elongated body having at least one aperture extending laterally and at least partially therethrough in a manner to form a gun having a bore and a primary firing chamber of a predetermined volume,

a primary charge of explosive of said predetermined volume located in said gun and substantially occupying said primary firing chamber,

a hollow projectile having a rear end and a forward cutting end and slidably disposed in said bore of said gun so that said rear end is adjacent said primary charge of explosive,

linking means interconnecting said projectile and said elongated body, and

means in said body for electrically igniting said primary charge of explosive;

the improvement in combination therewith including a base having a vent aperture and an inwardly hollowed exterior surface,

said base being mounted on said rear end of said projectile so that said hollowed surface faces said primary charge in a manner to provide an enlargement of said primary firing chamber,

a secondary charge of explosive disposed in said enlargement of said firing chamber and adjacent said primary charge, and

stoppering means removably located in said vent aperture.

10. Apparatus for obtaining a sample of earth substances from a subsurface earth formation of predetermined consolidation which is traversed by a borehole, said apparatus comprising an elongated body having at least one lateral aperture extending partially into said body in manner to form a gun bore and primary firing ch mber,

a hollow projectile having an open cutting end and a closed end with an inwardly hollowed outer surface, said projectile being slidably disposed in said bore with said closed end confronting said primary firing chamber in a manner such that said closed end of said projectile forms a secondary firing chamber in said gun,

linking means coupling said projectile to said gun, and

a propelling charge of selectively variable volume disposed in said primary and secondary firing chambers for discharging said projectile from said bore and into said earth formation a distance at least great enough to substantially fill said projectile with earth substances from said formation but not great enough to sever said linking means.

11. Apparatus of the character described in claim 10, wherein said propelling charge is at least large enough to substantially fill said primary firing chamber.

12. Apparatus of the character described in claim 10, wherein said propelling charge is composed of a primary propelling charge disposed in and substantially filling said primary firing chamber, and a secondary propelling charge separately disposed in and occupying at least a portion of said secondary firing chamber.

(References on following page) References Cited by the Examiner UNITED 1 4 OTHER REFERENCES STATES PATENTS Ser. No. 271,524, Schlumbenger (A.P.C.), published Hickman 102-49 May 25 1943 Laval 175 4 5 Blanchard 1754 X CHARLES E. OCONNELL, Primary Examiner.

Castel 175-4 Surbatovich 175 4 D. H. BROWN, Assistant Examiner. 

10. APPARATUS FOR OBTAINING A SAMPLE OF EARTH SUBSTANCES FROM A SUBSURFACE EARTH FORMATION OF PREDETERMINED CONSOLIDATION WHICH IS TRAVERSED BY A BOREHOLE, SAID APPARATUS COMPRISING AN ELONGATED BODY HAVING AT LEAST ONE LATERAL APERTURE EXTENDING PARTIALLY INTO SAID BODY IN A MANNER TO FORM A GUN BORE AND PRIMARY FIRING CHAMBER, A HOLLOW PROJECTILE HAVING AN OPEN CUTTING END AND A CLOSED END WTH AN INWARDLY HOLLOWED OUTER SURFACE, SAID PROJECTILE BEING SLIDABLY DISPOSED IN SAID BORE WITH SAID CLOSED END CONFRONTING SAID PRIMARY FIRING CHAMBER IN A MANNER SUCH THAT SAID CLOSED END OF SAID PROJECTILE FORMS A SECONDARY FIRING CHAMBER IN SAID GUN, LINKING MEANS COUPLING SAID PROJECTILE TO SAID GUN, AND A PROPELLING CHARGE OF SELECTIVELY VARIABLE VOLUME DISPOSED IN SAID PRIMARY AND SECONDARY FIRING CHAMBERS FOR DISCHARGING SAID PROJECTILE FROM SAID BORE AND INTO SAID EARTH FORMATION A DISTANCE AT LEAST GREAT ENOUGH TO SUBSTANTIALLY FILL SAID PROJECTILE WITH EARTH SUBSTANCES FROM SAID FORMATION BUT NOT GREAT ENOUGH TO SEVER SAID LINKING MEANS. 